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Old 29th July 2003, 10:16 AM   #1
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Default Gain of inverting amp

Hello All,
I am still in the process of making my first GC for an active system.
I have worked out that the amps for the tweeters only need to be app 20 watts rms.

I will be driving the system from my XA333ES SACD player which has a 2 v rms output which I will need to pad down.

From my initial calculations I have found I only need a gain of 9 to get full output with a 1 volt input.
Am I better to reduce the input voltage to 0.5 volts max and have a gain value of app 17.

Any help would be appreciated.

Regards
Blair
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Old 29th July 2003, 01:57 PM   #2
Nuuk is offline Nuuk  United Kingdom
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For use in an active speaker system where, presumably you will want the amps close to the drivers, I would recommend using the non-inverted design.

The alternative is to put a buffer before the inverted power amps.

I would just buld the amps with equal gain and then if you need to adjust the tweeter levels, put in some sort of volume control after.
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Old 30th July 2003, 06:11 PM   #3
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Hello Nuuk,
please excuse my ignorance if I ask why the topology of the non inverting amp is prefered to the inverted design for an active system.
Can you please explain.

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Blair
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Old 30th July 2003, 07:01 PM   #4
Nuuk is offline Nuuk  United Kingdom
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Quote:
Hello Nuuk,
please excuse my ignorance if I ask why the topology of the non inverting amp is prefered to the inverted design for an active system.
Can you please explain.
It is because with the inverted design, the feedback loop includes the items which preceed the amp, like the interconnects and the volume control.

As one of the big advantages of active systems is to have the amps as close to the drivers as possible, this would mean using long interconnects which could effect the performance of the IGC.

Of course, this may not be the case if you put the active crossovers immediately before the IGCs as they would act as a buffer, isolating the ICG circuit from the cables. But it needs somebody more experienced than I am to confirm this.
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Old 31st July 2003, 11:50 AM   #5
moamps is offline moamps  Croatia
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Quote:
Originally posted by Nuuk
It is because with the inverted design, the feedback loop includes the items which preceed the amp, like the interconnects and the volume control.
Hi,

Are you sure?

Regards
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Old 31st July 2003, 11:58 AM   #6
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Konnichiwa,

Quote:
Originally posted by Nuuk

It is because with the inverted design, the feedback loop includes the items which preceed the amp, like the interconnects and the volume control.
We have been there before and I must note again that while this view is readily promoted by a fairly high profile poster it is nevertheless absolutely and utterly wrong. The FEEDBACK loop is from the output to the inverting input, REGARDLESS if the Amplifier is inverting, noninverting or pseudo balanced Input.

You are talking about the input loop and that again is the same in all essentials for inverting and noninverting mode but differs for pseudo balanced. What MAY need to be addressed is the circuit stability with open input for the inverting design.

Sayonara
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Old 31st July 2003, 11:58 AM   #7
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Cool one of the big advantages of active systems is to have the amps as close to the drive

its an advantage - but not big......there are several much bigger advantages in an active setup.......
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Old 31st July 2003, 12:05 PM   #8
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If you are into very high-end (read: expensive) speaker cables, the advantage may be worth several 1000 dollars...

Jan Didden
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Old 31st July 2003, 12:22 PM   #9
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Old 31st July 2003, 12:38 PM   #10
moamps is offline moamps  Croatia
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Quote:
Originally posted by janneman
If you are into very high-end (read: expensive) speaker cables, the advantage may be worth several 1000 dollars...

Jan Didden

Longer interconnects are also expensive.
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